1. Field of the Invention
This invention relates to combustion heating apparatus, and, more particularly, to fireplace furnace apparatus in which the aesthetic appearance of a fireplace and the ability of the fireplace to burn relatively inexpensive wood is preserved and combined with the benefit of a furnace for heat collection and distribution throughout a structure in which the apparatus is installed.
2. Background of the Invention
Fireplaces have been used for many centuries. The original purpose of a fireplace was to provide heat for warming a structure, and to provide heat for cooking. There are obvious advantages to fireplaces, such as the ease of starting a fire and of adding fuel to the fire. Moreover, the fireplace burns primarily wood, which is a relatively plentiful and relatively inexpensive fuel.
When stoves were developed, they replaced fireplaces as a primary source of heat for cooking. In many instances, stoves, in conjunction with fireplaces, were used as the primary source of heat to heat a structure. When central heating units or furnaces were developed with duct work and, later, with forced air blowers powered by electric motors, fireplaces and stoves were replaced as the primary source of heat for heating a structure. Fireplaces then became primarily used for aesthetic purposes, rather than for functional purposes. They did, of course, provide heat for a room in which they were installed in a structure, but the heat thus provided, which is typical of fireplaces, is not evenly distributed throughout the room, and is a relatively inefficient source of heat. Most of the heat escapes up the chimney flue with the combustion gases.
One of the inherent problems with fireplaces of the prior art is that they require air (oxygen) for combustion and the air is drawn from the room in which the fireplace is installed. This means that in addition to radiating heat outwardly into the room, the heated air is in turn drawn back into the fireplace to provide the necessary oxygen for combustion.
Over the years, various designs of fireplaces have been developed to increase the efficiency of fireplaces as a source of heat. The most common design in use includes a structural metal interior shell, which comprises the fireplace box in which combustion takes place, with a space about the metal box and the space communicates with the room through a series of vents. The vents are typically situated relatively low and relatively high with respect to the fireplace. The cooler air from the room is drawn through the lower vents, heated from the fireplace, and circulates outwardly through the upper vents into the room. The air flows by natural convection of the heated air. However, such an arrangement, while producing generally more usable heat for the room in which the fireplace is installed, still draws back from the room the heated air for combustion purposes.
Prior art fireplaces use andirons to support fuel for burning. The fuel, generally wood logs, is disposed on the andirons for combustion pusposes. Air for combustion is typically drawn into the fireplace, both beneath the andirons, and accordingly upwardly through the fire, and directly into the fireplace and over the fuel burning on the andirons. The ashes or residue from the combustion of the fuel drops through the andirons and either onto the floor of the fireplace or into a bin for removal. The fuel, such as wooden logs, is accordingly disposed above the ashes so that the ashes will not smother or in any way hinder the combustion of the fuel on the andirons.
From open fireplaces, stoves are an evolutionary improvement for both heating and cooking purposes. The fire is enclosed in a metal enclosure which radiates heat outwardly and a surface is provided on which cooking utensils may be disposed. A grate is substituted for andirons for supporting fuel for combustion. Intake air may be carefully controlled to control combustion. The intake air may be more accurately contained than in an open fireplace and combustion may accordingly be more efficiently controlled.
Grates are more efficient and effective than andirons in holding fuel for combustion. However, fireplaces of the prior art do not incorporate a grate structure, as does the present apparatus.
There are potential problems with grate designs, however simple they may seem to be. For example, the spacing is an important consideration. The spacing determines the size of the burning particles of fuel which will fall through the grate. The larger the spacing, the larger the particles of fuel that will fall, and the smaller the spacing, the more the fuel will be burned before falling through the grates. On the other hand, if the space is too small, then there is a possibility, or even a likelihood, that the grate will become clogged with ashes and will cease to function as a grate should by letting ashes fall through.
A compromise to achieve the benefits of both types of grate systems has been to develop a movable grate in which the grate itself may be pivoted to allow the ashes and other burned residue to fall therethrough, or it may have the individual elements comprising the grates movable and by rotation or movement of the elements to allow the burned residue and ashes to fall therethrough.
To increase the efficiency of fireplaces, various designs have been employed, such as shown in U.S. Pat. Nos. 2,258,882 and 2,322,016. Convection currents are utilized in both patents to increase the efficiency of the heating by using the fireplace to heat auxiliary air moved around the fireplace structure. U.S. Pat. No. 2,789,554 also utilizes auxiliary air flow to increase the efficiency of a fireplace in inserting ductwork around the fireplace and above the fireplace in the chimney flue area. However, the three patents still utilize room air for combustion.
U.S. Pat. No. 3,845,754 is another version of attempts to overcome the deficiency of a fireplace by sealing the fireplace from the room in which it is installed and drawing combustion air from outside. This patent illustrates a concept of dual air flow paths, one path for combustion air and another path for heated air.
The present invention uses a dual path concept, and utilizes forced air to maximize the efficiency of the heat produced by combustion within the fireplace.